The present invention relates to an improvement of a pressure control valve to be provided in a ventilation path between a fuel tank and a canister for controlling an internal pressure of the fuel tank.
Japanese Patent Publication (Tokkai) No. 09-60744 has disclosed a pressure control valve (also called as a check valve, etc.) to be provided inside a ventilation path between a fuel tank and a canister for controlling an internal pressure of the fuel tank.
Such a conventional valve includes the first body, the second body, a positive pressure valve body, the first spring for urging the positive pressure valve, a negative pressure valve body, and the second spring for urging the negative pressure valve. That is, the conventional valve has relatively many parts, thereby requiring extra labor for assembly and making it difficult to reduce a cost.
In view of the problems of the conventional valve, an objective of the present invention is to provide a pressure control valve for a fuel tank with a minimal number of parts. The control valve opens properly a ventilation path between the canister and fuel tank when an inner pressure of the fuel tank reaches a high pressure level or a low pressure level.
Further objects and advantages of the invention will be apparent from the following description of the invention.
In order to attain the above objects, according to the first aspect of the invention, a pressure control valve for a fuel tank includes a valve chamber having the first communicating portion communicating with a canister and the second communicating portion communicating with the fuel tank; the first hollow valve member housed in the valve chamber to be vertically movable; and the second valve member housed in the first valve member to be vertically movable. A valve portion for closing the second communicating portion from the inside of the valve chamber and the first communicating hole passing through the valve portion are provided at a bottom of the first valve member. The second communicating hole is provided at an upper portion of the first valve member for communication between the inside of the first valve member and the valve chamber.
Further, the second valve member is disposed directly above the first communicating hole in a state that the second valve member is placed on a spacer portion formed around an edge of the first communicating hole so that the second valve member does not block the first communicating hole. Also, the valve portion for closing the second communicating hole from the inside of the first valve member is provided on the upper portion of the second valve member.
When an internal pressure of the fuel tank T increases due to fueling, the second valve member rises to close the second communicating hole. When the internal pressure of the fuel tank increases further and exceeds the pressure level increased by the fueling, the first valve member rises to open the second communicating portion.
With the above structure, when the internal pressure of the fuel tank is below the pressure level increased by the fueling, the first valve member closes the second communicating portion from the inside of the valve chamber by a weight of the first valve member. Also, the second valve member stays at a lower position by its own weight where the bottom of the second valve member is placed on the spacer portion formed around the edge of the first communicating hole. Accordingly, the second communicating portion communicates with the first communicating portion through the interior of the first valve member via the first communicating hole and the second communicating hole, thereby securing the air path between the canister and the fuel tank.
In other words, when the internal pressure of the fuel tank is lower than the pressure level increased by the fueling, it is possible to always create the air path between the canister and the fuel tank.
When the pressure in the fuel tank is increased to a predetermined value due to the fueling, only the second valve member rises by an upward pressure acting on the bottom of the second valve member through the first communicating hole to close the second communicating hole, so that the canister does not communicate with the fuel tank.
When the inside of the fuel tank becomes a predetermined high pressure state above the pressure level caused by the fueling, the second valve member rises by the upward pressure acting on the bottom of the second valve member through the first communicating hole to close the second communicating hole. At this time, the first valve member also rises by the pressure acting on the bottom of the first valve member through the second communicating portion to thereby open the second communicating portion, so that the gas flow can be formed between the canister and the fuel tank through the valve chamber.
According to the second aspect of the invention, a pressure control valve for a fuel tank includes a valve chamber including the first communicating portion communicating with a canister and the second communicating portion communicating with the fuel tank; a hollow first valve member housed in the valve chamber to be vertically movable; and a cylindrical second valve member housed in the first valve member to be vertically movable and having an open bottom end. A valve portion for closing the second communicating portion from inside of the valve chamber and the first communicating hole passing through the valve portion are provided at a bottom of the first valve member. The second communicating hole for communication between the inside of the first valve member and the valve chamber is provided at an upper portion of the first valve member.
The second valve member is disposed directly above the first communicating hole to close the first communicating hole. A valve portion for closing the second communicating hole from the inside of the first valve member is provided on an upper portion of the second valve member. Further, an airflow portion for communicating the inside of the second valve member and the inside of the first valve member is formed on a side of the second valve member.
When the internal pressure of the fuel tank increases due to the fueling, the second valve member rises to close the second communicating hole. When the internal pressure of the fuel tank increases further and exceeds the pressure level increased due to the fueling, the first valve member rises to open the second communicating portion.
With the structure described above, when the pressure in the fuel tank is less than the pressure level increased due to the fueling, the first valve member blocks the second communicating portion from the inside of the valve chamber by its own weight. Also, the second valve member closes the first communicating hole from the inside of the first valve member by its own weight. However, the second communicating portion communicates with the first communicating portion through the interior of the first valve member via the interior of the second valve member communicating with the first communicating hole and the airflow portion, thereby securing the airflow between the canister and the fuel tank.
In other words, when the internal pressure of the fuel tank is lower than the pressure level increased by the fueling, it is possible to always create the air path between the canister and the fuel tank.
When the pressure in the fuel tank is increased to a predetermined value due to the fueling, only the second valve member rises by the upward pressure acting on the bottom of the second valve member through the first communicating hole to close the second communicating hole, so that the canister does not communicate with the fuel tank.
When the inside of the fuel tank becomes a predetermined high pressure state above the pressure level caused by the fueling, the second valve member rises by the upward pressure acting on the bottom of the second valve member through the first communicating hole to close the second communicating hole. At this time, the first valve member also rises by the pressure acting on the bottom of the first valve member through the second communicating portion to thereby open the second communicating portion, so that the gas flow can be formed between the canister and the fuel tank through the valve chamber.
According to the third aspect of the invention, the pressure control valve for the fuel tank according to the first and second aspects of the invention further includes a lower chamber with a bottom of the valve chamber as a top wall thereof to be disposed in the fuel tank. The valve chamber communicates with the lower chamber through the second communicating portion. Further, a floating member constituting a cut valve is disposed in the lower chamber for closing the second communicating portion from the lower chamber side when the fuel flows into the lower chamber.
With the structure described above, the cut valve with a function for controlling the internal pressure of the fuel tank is constructed through the first valve member and the second valve member with the minimum number of the parts.